Distributed tracing is essential for debugging and enhancing the performance of systems by linking traces across services to provide a comprehensive view of how requests flow through a system. In a modern Next.js application, distributed tracing is exemplified through a practical guide that integrates Highlight, an external service, by passing HTTP headers like x-highlight-request. The process involves a React web client initiating an HTTP Fetch request, a Next.js API function associating session and request IDs, and a Golang service using the Highlight chi SDK to handle the headers. The guide demonstrates how to implement client-side integration with <HighlightInit /> and wrap Next.js API functions using AppRouterHighlight, ensuring all three components—web client, Next.js API, and Golang backend—are unified under one Highlight project. The setup allows for visualization of data in Highlight, offering a detailed view of trace spans and supporting session replay through the distributed call stack. Additionally, the guide mentions the possibility of using OpenTelemetry's W3C traceparent header for an alternative tracing method.